By October 1st, there will likely be some kind of student housing offered, although it is more informal at some schools than others. The typical recommendation I've been given is to reserve a room at a hotel based on three important criteria, in no particular order:
1) Proximity to Campus/Admissions Office. Walking 0.5-1.0 miles to the interview makes practical sense (no last minute panic over a taxi running late), and is a very relaxing way to start an otherwise unrelaxed day.
2) Free Cancellation. This way, if student housing opens up at any point in the week prior to the interview, you can cancel your reservation with no harm done. Book early for peace of mind, but allow yourself the ability to be flexible should other alternatives arise.
3) Accommodations. (I know I said no order, but this is definitely the least important). I'm
not talking about "star-rated" hotels. Frankly, I couldn't care how many stars a hotel has, as long as my door locks at night. But (free) Wi-Fi is
imperative for reviewing the school's curriculum and resources the night before, just as a refresher (obviously don't stay up until 1am "cramming" for your interview...). Additionally, some hotels might offer to press a suit/skirt/whatever for you the night before, which is quite handy.
To answer your question more directly, however,
Feinberg posts a list of potential hotels, all of which are quite pricy. I would have to look around a bit more on expedia or other relevant sites for cheaper options, i.e. red roof inn, motel 6, w/e (perhaps
this one if I really wanted to treat myself, although
still a bit out of my price range).
Wish your son good luck from me!